Method of producing jet fuel by upgrading light catalytic cycle oil

ABSTRACT

JET FUEL IS PRODUCED BY EXTRACTIVE DISTILLATION OF LIGHT CATALYST CYCLE OIL BOILING IN THE JET FUEL BOILING RANGE USING CATALYST FRACTIONATOR BOTTOMS AS THE SOLVENT, AND SUBSEQUENT FINISHING SUCH AS MILD HYDROFINING OF LOWAROMATICS RAFFINATE.

vMarch 26, 19.74

D. W. DEED METHOD OF PRODUCING JET FUEL BY UPGRADING ET AL LIGHT CATALYTIC CYCLE OIL Filed April 13, 1972 United States Patent O U.S. Cl. 20S-211 9 Claims ABSTRACT F THE DISCLOSURE Jet fuel is produced by extractive distillation of light catalytic cycle oil boiling in the jet fuel boiling range using catalyticfractionator bottoms as the solvent, and subsequent finishing such as mild hydroning of the lowaromatics rainate.

The present invention is directed to a method of producing jet fuel. More particularly, it is directed to a method of upgrading light catalytic cycle oil to jet fuel specifications. In its more specific aspects, the invention concerns a method of reducing the aromaticscontent of catalytic cycle oil boiling in the jet fuel boiling range to obtain an upgraded jet fuel base which, upon mild hydrofining, may be converted to jet fuel.

The increasing demand for jet fuel may outstrip the readily available supply of virgin stocks within the next few years. Accordingly, the production of synthetic jet fuel by economically feasible methods is a matter of rather urgent priority. Two basic synthetic procedures have been proposed. The first involves high pressure hydrogen processing aimed at aromatics saturation, e.g., hydrocracking virgin gas oil or hydrogenating light catalyticl cycle oil. These methods have the advantage of being essentially single-step processes, but the need for extreme conditions of high pressure and temperature results in high operating costs. The second basic procedure is the segregating of light catalytic cycle oil into an aromatic concentrate extract and a low-aromatics rafiinate, and subsequent upgrading of the rainate to jet fuel by relatively mild hydrogen treating. The second procedure eliminates the need to operate at high pressures, but, since it is a two-step process, operating costs remain high.

It is an object of this invention to produce a synthetic jet fuel from light catalytic cycle oil. It is a further object of this invention to produce a jet fuel by a method which is economically attractive, i.e. at a cost which is competitive with the current costs of producing jet fuel from virginstocks. Other objects and advantages of this invention will be apparent from the detailed description which follows.

According to this invention, light catalytic cycle oil boiling in the jet fuel boiling range; e.g., 320 to 520 F., preferably 330 to 425 F., is subjected to extractive distillation using catalytic fractionator bottoms as the extractive solvent. The light catalytic cycle oil is thus separated into two phases, an aromatics rich extract and a low-aromatics raflinate. The rainate is then subjected to a finishing step such as hydroning under relatively mild conditions to obtain jet fuel as the product. Separation of catalytic cycle oils into high-aromatics and lowaromatics phases by means of solvent extraction is well known in the art, but the solvents heretofore used have been low boiling polar compounds such as ethanol, methanol, phenol, furfural, sulfur dioxide, acetonitrile, etc. The method of the present invention employs catalytic fractionator bottoms for this purpose; these are readily available in any refinery operation and, by their use, a signicant saving in costs will result. The separa- Cce tion is especially eifective for removal of two-ring aromatics, which are harmful to burning qualities of jet fuel.

Catalytic cycle stock is the term used to designate the fraction or fractions obtained in catalytic cracking operations having a boiling range above the gasoline range. In the operation of a catalytic cracking unit, a gaseous product (gasoline), catalytic cycle stock, and bottoms fraction are obtained. Characteristics of the catalytic cycle stock are an index of refraction measured at 67 C. within the range of about 1.4900 to about 1.5200 and a specific gravity within the range of about 17 to about 26 API (60 F.). It boils in the range of about 320 to about 10l5 F., with a substantial portion thereof boiling below about 900 F. The term light catalytic cycle oil as used herein is that fraction or fractions of catalytic cycle stock boiling at the lower ranges, i.e. about 320 to 520 F., and preferably between about 330 and 425 F. More particularly, the light catalytic cycle oil used in the practice of this invention has the characteristics set forth in Table l.

TABLE 1,-LIGHT CATALYTIC CYCLE OIL Nominal boiling range: 320-520 F. Actual IVT: 30Go-350 F. Actual FVT: 400550 F.

Range Example Composition, vol. percent:

Paratiins 5-50 30 Olens 5-25 10 Naphthenes 5-50 l0 Aromatics 20-70 50 TABLE 2.CATALYTIC FRACTIONATOR BOTTOMS Nominal boiling range: 800+ F. Actual IVT: 400-600 F.

Range Example Composition, vol. percent:

al'iins Par 0-10 5 Olens 0-5 1 Naphthenes 0-10 4 Aromatics. 60-95 90 The major portion of the aromatics must be multi-ring aromatics, in order to render the fractionator bottoms an effective solvent.

The extractive distillation operation is suitably conducted by introducing the light catalytic cycle oil into the lower portion of an elongated column while the catalytic fractionator bottoms solvent is introduced into the upper portion thereof. The cycle oil and the solvent move countercurrently through the column wherein effective contact between the countercurrently moving phases is generally secured by distributing and contacting means such as bell cap trays, contact masses, distributing plates, pierced plates, and the like. Temperature and pressure conditions are maintained in the column by suitable means to secure the formation of an extract phase and a rainate phase. The extraction may be carried out at temperatures between about F. and about 750 F., preferably between about 200 F. and 650 F. The solvent-to-cycle oil ratio may be in a range of about 2:1 to about 6:1, preferably about 4:1.

The raffinate yield is a function of the composition of the light catalytic cycle oil feed and the fractionator bottoms solvent and of the extraction conditions. The yield is generally about 20 vol. percent to 70 vol. percent of the light catalytic cycle oil feed and contains no more than about 20%, preferably no more than about 15%, of aromatics.

If a hydroiining operation is used as the :finishing step, the preferred catalyst is cobalt molybdate on a suitable support such as alumina. Other hydroning catalysts such as but not limited to molybdenum disulfide, nickel-molybdenum, nickel-cobalt molybdate, nickel-tungsten sulfide, and iron-cobalt molybdate deposited on suitable bases may be employed. Temperatures may range from about 500 F. to about 700 F. with preferred temperatures from about 600 F. to about 630 F. Pressures may range from about 600 to 1000 p.s.i. with preferred pressures within the range from about 650 to about 750 p.s.i. Space velocities may range from about 0.5 to about 3.0 v./v./hr., with preferred space velocities within the range from about 1 to about 2. Hydrogen is suitably employed in the hydroning operation in the amount from about 100 to about 1000 s.c.f./bbl., with a preferred amount of hydrogen from about 500 to about 600 s.c.f./ bbl. In this operation, the sulfur content of the raffinate should be reduced to about 100 to 1000 p.p.m.

The present invention will be further illustrated by reference to the drawing in Which the single ligure is a flow diagram of a preferred mode. Referring now to the drawing, numeral 11 designates a charge line by way of which a catalytic cracking cycle stock is introduced into the system from a catalytic cracking operation which may be of the uidized bed type or of the disperse phase or transfer line reaction type. The cycle stock is introduced into a distillation zone 12, illustrated as a single distillation tower, but which may be a plurality of distillation towers. Zone 12 is provided with a suitable internal vapor-liquid contacting means and other auxiliary means such as means for inducing reflux, condensing and cooling means, and the like. Zone 12 is also provided with a heating means 13 for controlling temperatures and pressures. Line 14 is provided by way of which an overhead fraction is removed from zone 12, and line 15 by way of which a heavier fraction is discharged. The light catalytic cycle oil fraction is removed by line 16. It is this fraction which constitutes the feed to the solvent extractor, from which the jet fuel base is obtained.

The light catalytic cycle oil in line 16 is discharged thereby into a solvent extraction zone 17 into which there is introduced by way of line 18 the liquid catalytic fractionator bottoms as solvent. Conditions are adjusted in zone 17 for obtaining an extract phase and a raffinate phase. The extract phase is discharged by line 19 for removal of solvent and further processing, e.g. into mogas, if desired. The raffinate phase is discharged by line 20 into a heater 24 for increasing the temperature of the raffinate to the hydroning range. The heated rainate discharges by line 25 into a hydroining zone 26 containing a bed 27 of hydroning catalyst such as 3.7% COO and 13.1% M003 on alumina. Under the conditions of zone 27, the rainate is hydrotined to reduce its sulfur content to less than 1000 p.p.rn. The hydroined product, jet fuel, is discharged via line 28. The extract phase discharged by line 19 goes to a stripper 21 for separation into the fractionator bottoms solvent which goes by line 22 back to the top of the extractive distillation zone at point 18. The aromatic concentrate removed via line 23 can be further processed into high octane gasoline or used for other purposes related to its high content of aromatics.

In order to illustrate the invention further, extractive distillation is performed to recover jet fuel base from a light catalytic cycle oil boiling in the range 330 to 425 1:'. The light catalytic cycle oil contains 44 LV percent of aromatics. The fractionator bottoms to be employed as solvent has a boiling point of 900 F. The components of the light catalytic cycle oil feed and the fractionator bottoms solvent are set forth in Table 3.

TABLE 3.-FEED AND LEAN-OIL TO EXTRACTIVE DISTIL- LATION Feed--LC CO kerosine cut: 44.1 vol. percent aromatics, 47.1 vol. percent olens, 8.8 vol. percent parafns Vol. Boiling Components percent point, F.

1,3,5-trlmethylbenzene 11. 4 329 l-decene 19. 7 339 B-methylnonane 2. 2 334 Total light 33. 3

1,2,4,5tetramethylbenzene 14. 5 386 l-undecene 16. 7 379 2,5-di-methyldecane... 2. 1 388 Total medium 33. 3

Naphthalene 18. 2 421 l-dodecene 10. 7 416 n-D odecane 4. 5 421 Total heavy 33. 4

Total components 100. 0

Lean oil-Cat. fractionator bottoms: vol. percent aromatics Condensed ring aromatic 100 899 TABLE 4.SUPERFRACTIONATION vs. EXTRACTIVE DISTILLATION [20 rectifylng trays, 20 stripping trays] Fractionati on Extractive distillation Leanoillfeed 6. 7:1 10; 1 Reboll heat (MM Btu./b.ld.) 0. 87 0. 58 0. 87 Overhead, mol. percent 59. 3 59. 3 59. 3

Overhead composition: l

Light aromatic 19. 2/100 17. 3/100 17. 3/100 Light olefin..- 33. 3/100 29. 9/100 29. 9/100 Light paran. 3. 7/100 3. 4/100 3. 4/100 Intermediate aromatic- 24. 3/93. 4 4.3/19. 2 4 1/ 18. 6 Intermediate olefin 16. 8/59. 6 25. 3/100 25. 3/100 Intermediate paran. 0. 2/5. 7 3. 2/100 3. 2/100 Heavy aromatic. 2. 5/8. 1 Heavy olefin- 16. 2/100 16. 2/100 Heavy paran.. 0. 4/5. 8 0. 6/9. 1

Total 100. 0/59. 2 100. 0/ 65. 9 100. 0/65. 9 Total aromatics 64. 0/61. 8 21. 6/32. 3 21. 4/32. 0

Bottoms, mol percent 40. 7 40. 7 40. 7

Bottoms composition: 2 Light aromatic.

Light nl afin Light paran Intermediate aromatic 0. 2/6. 6 34. 1/80. 8 34 5/81 4 Intermediate olen; 16. 5/40. 4 Intermediate paraffin 4. 9/94. Heavy aromatic 41. 1/91 9 53 5/100 53. 5/100 Heavy olefin 26. 3/100 Heavy paran.- 11. 0/100 12. 4/94. 2 12. 0/90. 9

Total 100. 0/40. 8 100. 0/34. 1 100. 0/34. 1

Total aromatics. 4l. 3/38. 2 87. 1/67. 7 88. 0/68. 0

l Volume percent of overhead/volume percent of component. 2 Volume percent oi bottoms/volume percent of component.

aromatics and a ranate phase low in aromatics, and subjecting said raffinate to a finishing step.

2. A method according to claim 1 wherein the light catalytic cycle oil has a boiling range of from about 320 to about 520 F. and the catalytic fractionator bottoms have a boiling point of about 900 F.

3. A method according to claim 2 in which the light catalytic cycle oil has a boiling range of from 330 to 425 C.

4. A method according to claim 2 in which the extraction step comprises extractive distillation carried out at a temperature within the range of from about 150 to about 750 F. and at a solvent-to-cycle oil ratio of from about 2:1 to about 6:1.

5. A method according to claim 4 in which the extractive distillation is carried out at a temperature within the range of from about 200 to about 650 F. and at a solvent-to-cycle oil ratio of about 4: 1.

6. A method according to cla-im 2 in which the finishing step is a hydroining operation.

7. A method according to claim 6 in which the hydrofning is carried out at temperatures within the range of from about 500 F. to about 700 F., at a pressures within the range of from about 600 to about 1000 p.s.i., and at a space velocity of from about 0.5 to about 3.0 v./v./hr.

8. A method according to claim 7 in which the hydroning is carried out in the presence of an alumina sup References Cited UNITED STATES PATENTS 3,620,961 11/ 1971 Ireland 20S-15 3,328,288 6/ 1967 Streed 208-87 3,085,062 4/ 1963 Anaostasoi 20S-313 2,93 7,13 5 5/ 1960 Middleton 208-87 2,053,485 9/ 103 6 Lindeke et al. 20S-337 3,331,766 7/1967 Young 208-87 3,201,345 8/1965 Hamilton et al 208-143 DELBERT E. GANTZ, Primary Examiner C. E. SPRESSER, I R., Assistant Examiner U.S. Cl. X.R. 

